Scientists have been studying Middle Eastern respiratory (MERS) virus, a new virus that first presented in an older Saudi Arabian man in June 2012 [source: Brown]. He died from pneumonia and respiratory failure with symptoms resembling SARS, but the viruses didn't match.

The race was on to identify the source of this new virus. After sequencing the virus's genome, scientists found its closest relative belonged to a virus found in bats in rural Saudi Arabia. There are several areas where bats roost near people and feed on nearby fruit. So, it's highly likely the MERS virus moved from bats to humans, probably transmitted through excrement on or near the fruit trees. As of fall 2014, MERS had infected more than 800 people and killed nearly 300 [source: Watson and Hastwell].

Another virus that made the jump from animals to humans is HIV. Scientists believe the spillover began when humans began populating the forests in West Africa to find food. Demand for meat led to slaughter of chimpanzees, a reservoir for HIV (meaning that they carry the virus but aren't affected by it). However, that virus can jump to a different species and then cause complete chaos. People who ate chimpanzee meat, or slaughtered the chimps and got the infected blood in their own wounds, contracted the virus. The virus moved slowly and was not identified until the outbreak in the late 1980s in the United States [source: Laurance].

Scientists and researchers keep an eye on on current and emerging infectious diseases through the World Health Organization (WHO) in an attempt to stop the spread of dangerous animal-to-human viruses before they become epidemic.

Some animals and insects are more likely to carry infectious disease than others. These include:

The best way to avoid contracting a virus from an animal is prevention — taking steps to avoid the risk of infection. Everyone should take care to prevent catching a virus, but people with compromised immune systems must be even more vigilant. This includes children under age 5, the elderly, pregnant women and those with autoimmune system diseases.

In our everyday lives, the most common way for zoonotic disease to spread is through mosquito or tick bites. Using window screens, insect repellent and protective clothing helps reduce the chance of bites. So does removing any standing water around your home, as it's a breeding ground for mosquitoes.

Other places people may come into contact with infected animals include petting zoos, animal displays, farms, state fairs and wooded areas. Be sure to wash hands thoroughly if you touch any animals, and avoid direct contact with them out in nature. If you are bitten or scratched by an animal you don't know, get medical attention immediately and report the animal to authorities.